There probably is no organ with a greater impact on human health than the immune system. The cells of the immune system patrol nearly every site in the body in order to defend against pathogens. Dysregulation of immune function can occur, however, and may result in immunodeficiency, autoimmunity or allergy. The last several decades have seen an explosion of knowledge regarding the normal functioning of the immune system, how immune reactions may go awry, and how immune modulation may be used for therapeutic advantage. The Gordon Research Conference (GRC) on Immunochemistry and Immunobiology has been held regularly since 1966. The next meeting is planned for May 2010, at Les Diablerets, Switzerland. The philosophy of the GRC organization has helped to shape the unique character of this longstanding meeting series, which is distinguished by several important factors. First, it is a prestigious meeting that attracts the most accomplished investigators in the field. This is not at the expense of junior investigators, who are also well represented in the program as invited speakers. Second, it is a relatively small meeting (less than 150 attendees), held in an intimate setting with attendees staying at the meeting place. Moreover, at Gordon Conferences invited speakers are expected to stay for the entire meeting and their expense reimbursements depend on abiding by this policy. The location and the ethic of attending the entire meeting allows for close contacts between junior investigators and their more senior colleagues. Third, the nine half day meeting sessions cover the broad field of immunology, focusing on the most intensely investigated "hot" issues. Other meetings that broadly cover immunology are very large, while smaller immunology meetings almost always focus on subtopics such as immune development or cytokines. Fourth, a strong emphasis is placed on the presentation of unpublished material. Fifth, the meeting has a democratic organization with input from a great many experts leading to the formation of the program. In particular, participation by women and underrepresented minorities is actively sought. In this application, we seek support for this important and prestigious conference. This is a proposal for NIH support for a meeting to summarize the latest advances in understanding the immune system, particularly to support the travel of junior investigators. The immune system protects us against infections every day, but it can also function improperly, causing allergies or chronic diseases such as type I diabetes and multiple sclerosis. The meeting will bring together leading experts in the world for an intimate and intense exchange of ideas, techniques and concepts on both basic research and more applied topics that will help to advance knowledge in the field.